Low traction energy conserving fluids containing base stock blends

ABSTRACT

A lubricant composition including a first fluid having a viscosity from 150 cSt to 2000 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.01 to 0.025 (MTM TC Method), and a second fluid having a viscosity from 1 cSt to 30 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.008 to 0.015 (MTM TC Method). The second fluid is miscible with the first fluid. The traction coefficient of the lubricant composition is lower than the traction coefficient of the first fluid and the traction coefficient of second fluid, as determined by the MTM TC Method. Provided is also a method of reducing the traction coefficient of a lubricant composition.

FIELD

This disclosure relates to lubricating fluids and oil formulations which provide exceptionally low traction, a method of lowering traction coefficients in lubricating compositions, and to uses of such compositions.

BACKGROUND

Environmental regulations and increased energy cost have made improvement of energy efficiency one of the most prominent trends among equipment builders and end users of industrial and mobile equipment. Energy efficiency improvements come from modifications in mechanical design, use of advanced materials and changes in the way equipment is operated. Innovative solutions also come from the lubricant industry, as many of the energy loss mechanisms are related to lubrication.

One of the most prominent functions of a lubricant is keeping the moving mechanical parts apart. Full separation under load leads to a situation called elastohydrodynamic lubrication (EHL).

EHL is the mode of lubrication that exists in non-conforming concentrated contacts. Examples include the contact between meshing gear teeth used in hypoid axles, worm gears, etc. and between the components in a rolling element bearing. In these contacts the load is supported over a very small contact area which results in very high contact pressures. As lubricants are drawn into the contact zone by the movement of the component surfaces, the lubricant experiences an increase in pressure. Pressures on the order of 1 GPa and above are common in EHL contacts. Most lubricating oils exhibit a large increase in viscosity in response to higher pressures. It is this characteristic that results in the separation of the two surfaces in the contact zone.

If there is relative sliding between the two contacting surfaces in the central contact region, the lubricant is sheared under these high-pressure conditions. The shearing losses depend on how the oil behaves under these extreme conditions. The properties of the oil under high pressure, in turn, depend on the type of base stocks used in the manufacture of the finished lubricant. The generation of the EHL film is governed by what happens in the inlet region of the contact; however, the energy losses are governed by what happens when the lubricant is sheared in the high-pressure central contact region.

The resistance of the lubricant to the shearing effects within an EHL contact is referred to as traction. Even though ultimately this force would be classified as friction, the distinct name allows tribologists and lubrication engineers to distinguish it from friction due to surface interactions. The traction response is dominated by the behavior of the lubricant under shear in the central high contact pressure region of an EHL contact. The traction properties generally depend on the base stock type.

Traction coefficients can be defined as the traction force divided by the normal force. The traction force is the force transmitted across a sheared EHL film. The normal force or contact load is the force of one element (such as a roller) pushing down on a second element. Therefore, the traction coefficient is a non-dimensional measure of the shear resistance imparted by a lubricant under EHL conditions. Lower traction coefficients result in lower shearing forces and hence less energy loss if the two surfaces are in relative motion. Low traction is believed to be related to improved fuel economy, increased energy efficiency, reduced operating temperatures, and improved durability. In certain applications where energy loss is dominated by shearing of a lubricant (such as worm gearbox), energy efficiency directly correlates with the traction coefficient.

This direct correlation makes traction coefficient very useful for lubricant formulators. Traction is usually measured in a ball-on-disc machine (e.g. MTM) and has been targeted in lubricant development helping advance synthetic base stocks (PAOs, synthetic esters and PAGs) and develop technologies such as extreme modal blending. In a family of fluids with similar chemical composition, traction tends to correlate with viscosity. Lubricating products are sold at a given viscosity point (called a grade). Typically traction increases with viscosity. It has been shown that traction of a blend can be minimized by blending basestocks with different viscosities. Traction coefficient of a blend can be lower than traction predicted as a linear combination of traction coefficient of straight basestocks with corresponding viscosity. It is however, higher than the traction coefficients of its components. When taken to its extreme this approach uses basestocks with highest and lowest practical viscosities and is called extreme modal blending as described, for example, in U.S. Patent Application Publication No. 2007/0298990 A 1 and U.S. Pat. No. 7,683,013.

There is a need for lubricating basestocks and additives capable of lowering traction in a lubricating oil so as to improve energy efficiency, particularly in industrial and automotive applications.

The present disclosure also provides many additional advantages, which shall become apparent as described below.

SUMMARY

This disclosure is directed to high and low viscosity fluid blends that have the ability to impart low traction characteristics to compositions incorporating the fluids, and to a method of modifying the traction coefficient of a composition by the addition thereto of high and low viscosity fluids. The disclosure is also directed to the use of high and low viscosity fluids in compositions, and also the use of said compositions with machine elements in which sliding and rolling is observed.

In an embodiment, a first fluid of at least one Group I-V basestock may be blended with a second fluid of at least one other Group I-V basestock, optionally with additives (e.g., viscosity index (VI) improvers). In other embodiments, the lubricant compositions of this disclosure may be a blend of a first fluid of at least one Group I-V basestock and a second fluid of at least one other Group I-V basestock, and may be further characterized by the absence of additives (e.g., VI improvers).

In another embodiment, the lubricant compositions of this disclosure may be a blend of a first fluid of at least one Group V basestock (e.g., ester) and a second fluid of at least one other Group V basestock (e.g., ester).

In an embodiment, the lubricant compositions of this disclosure may be a blend of a first fluid having a viscosity from 150 cSt to 2000 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.01 to 0.025 (MTM TC Method as described herein), and a second fluid having a viscosity from 1 cSt to 30 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.008 to 0.015 (MTM TC Method).

In another embodiment, a lubricant composition comprises a first fluid having a viscosity from 150 cSt to 2000 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.01 to 0.025 (MTM TC Method), and a second fluid having a viscosity from 1 cSt to 30 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.008 to 0.015 (MTM TC Method). The second fluid is miscible with the first fluid. The traction coefficient of the lubricant composition is lower than the traction coefficient of the first fluid and the traction coefficient of second fluid, as determined by the MTM TC Method.

In an embodiment, the method of this disclosure involves reducing the traction coefficient of a lubricant composition. The method comprises blending a first fluid having a viscosity from 150 cSt to 2000 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.01 to 0.025 (MTM TC Method), with a second fluid having a viscosity from 1 cSt to 30 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.008 to 0.015 (MTM TC Method). The second fluid is miscible with the first fluid. The traction coefficient of the lubricant composition is lower than the traction coefficient of the first fluid and the traction coefficient of second fluid, as determined by the MTM TC Method. The method of this disclosure provides for increasing the efficiency of gear systems and/or improving the fuel efficiency of machines including the gear systems.

In accordance with this disclosure, low traction coefficient lubricants are provided that are suitable for use in machines with various degrees of sliding, i.e., non-conforming concentrated contacts, such as with roller and spherical bearings, hypoid gears, worm gears, and also conforming contacts such as thrust and journal bearings, and the like. Fluids that exhibit low traction properties will reduce the losses in components that contain sliding EHL contacts.

It has been surprisingly found that, in a lubricant composition comprising a first fluid, e.g., ester, having a viscosity from 150 cSt to 2000 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.01 to 0.025 (MTM TC Method), and a second fluid, e.g., ester, having a viscosity from 1 cSt to 30 cSt at 40° C. (ASTM D-0.445) and a traction coefficient from 0.008 to 0.015 (MTM TC Method), the traction coefficient of the lubricant composition is lower than the traction coefficient of the first fluid and the traction coefficient of second fluid, as determined by the MTM TC Method.

Further objects, features and advantages of the present disclosure will be understood by reference to the following drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 lists the viscosity and traction coefficient of neat ester base stocks used in the Examples.

FIG. 2 graphically shows the dependence of traction coefficient on the composition of a polyalphaolefin (PAO) blend.

FIG. 3 graphically shows the dependence of traction coefficient on the composition of an ester blend (i.e., Priolube™ 2087+Synative™ ES 3235) as shown in the Examples.

FIG. 4 graphically shows the dependence of traction coefficient on the composition of various esters and ester blends as shown in the Examples. In each graph, the “y” axis is the traction coefficient and the “x” axis is the content of the high viscosity ester (wt. %) in the blend.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

The disclosure is directed to low traction coefficient lubricants and lubricant compositions in the preparation of finished gear, transmission, engine, and industrial lubricants and in a preferred embodiment are used as lubricants for non-conforming concentrated contacts with high sliding such as spur gears, helical gears, hypoid gears, bevel gears, worm gears and the like.

As used herein, traction coefficient is determined by a PCS Instruments Mini-Traction Machine (MTM) using standard steel specimens, a lubricant temperature of 100° C., a 1.0 GPa peak contact pressure, a lubricant entraining velocity of 2 ms, and a 25% slide-to-roll ratio (hereinafter “MTM TC Method”). Suitable MTM testing properties include, for example, 0.1 to 3.5 GPa, peak contact pressure, −40° C. to 200° C. lubricant temperature, and a lubricant entraining velocity of from 0.25 to 10.0 m/s. Other methods can be used to determine traction coefficient provided the measurements are consistent with a given method in making any comparisons. As used herein, viscosity is determined by ASTM D-445.

In an embodiment, the low traction coefficient lubricants comprise blends of a high viscosity fluid and a low viscosity second fluid. The second fluid is miscible with the first fluid. The traction coefficient of the lubricant composition is lower than the traction coefficient of the first fluid and the traction coefficient of second fluid. In an embodiment, the low traction coefficient lubricants of this disclosure comprise a first fluid having a viscosity from 320 cSt to 1700 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.01 to 0.020 (MTM TC Method), and a second fluid having a viscosity from 3.2 cSt to 16 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.008 to 0.010 (MTM TC Method). The second fluid is miscible with the first fluid. The traction coefficient of the lubricant composition is lower than the traction coefficient of the first fluid and the traction coefficient of second fluid, as determined by the MTM TC Method.

In yet another embodiment they are used to formulate viscosity grade lubricants, e.g., those that meet the requirements of SAE J306, the viscosity classification for automotive gear oils, or the requirements of ISO 3448, the industrial oil classification system.

In the lubricant compositions of this disclosure, the high viscosity first fluid has a viscosity from 150 cSt to 10,000 cSt at 40° C., preferably from 150 cSt to 2000 cSt at 40° C., more preferably from 320 cSt to 1700 cSt at 40° C., and even more preferably 350 cSt to 1700 cSt at 40° C. (ASTM D-445). The high viscosity first fluid has a traction coefficient from 0.008 to 0.025, preferably from 0.09 to 0.02, and more preferably from 0.010 to 0.02 (MTM TC Method). Viscosities used herein are kinematic viscosities unless otherwise specified, determined at 40° C. or 100° C. according to any such suitable method for measuring kinematic viscosities, e.g., ASTM D445.

In the lubricant compositions of this disclosure, the low viscosity second fluid has a viscosity from 1 cSt to 30 cSt at 40° C., preferably from 1.0 cSt to 20 cSt at 40° C., more preferably from 1.5 cSt to 20.0 cSt at 40° C., and even more preferably 2.5 cSt to 16 cSt at 40° C. (ASTM D-445). The low viscosity second fluid has a traction coefficient from 0.008 to 0.015, preferably from 0.008 to 0.011, and more preferably from 0.008 to 0.01 (MTM TC Method). Viscosities used herein are kinematic viscosities unless otherwise specified, determined at 40° C. or 100° C. according to any such suitable method for measuring kinematic viscosities, e.g., ASTM D445.

It is important that the first and second fluids be miscible with each other to comprise a clear fluid. The term miscible takes its ordinary meaning of “the ability to mix in all proportions”. For purposes of this disclosure, miscibility is determined at 25° C. and 1 atm.

Fluids (e.g., base stocks) that can meet these criteria according to the present disclosure are varied. They may fall into any of the well-known American Petroleum Institute (API) categories of Group I through Group V as described herein.

A wide range of lubricating oil base stocks is known in the art. Lubricating oil base stocks that are useful in the present disclosure are both natural oils and synthetic oils. Natural and synthetic oils (or mixtures thereof) can be used unrefined, refined, or rerefined (the latter is also known as reclaimed or reprocessed oil). Unrefined oils are those obtained directly from a natural or synthetic source and used without added purification. These include shale oil obtained directly from retorting operations, petroleum oil obtained directly from primary distillation, and ester oil obtained directly from an esterification process. Refined oils are similar to the oils discussed for unrefined oils except refined oils are subjected to one or more purification steps to improve the at least one lubricating oil property. One skilled in the art is familiar with many purification processes. These processes include solvent extraction, secondary distillation, acid extraction, base extraction, filtration, and percolation. Rerefined oils are obtained by processes analogous to refined oils but using an oil that has been previously used as a feed stock.

Groups I, II, III, IV and V are broad categories of base oil stocks developed and defined by the American Petroleum Institute (API Publication 1509; www.API.org) to create guidelines for lubricant base oils. Group I base stocks generally have a viscosity index of between 80 to 120 and contain greater than 0.03% sulfur and less than 90% saturates. Group II base stocks generally have a viscosity index of between 80 to 120, and contain less than or equal to 0.03% sulfur and greater than or equal to 90% saturates. Group III stock generally has a viscosity index greater than 120 and contains less than or equal to 0.03% sulfur and greater than 90% saturates. Group IV includes polyalphaolefins (PAO). Group V base stocks include base stocks not included in Groups I-IV. The table below summarizes properties of each of these five groups.

Base Oil Properties Saturates Sulfur Viscosity Index Group I  <90 and/or  >0.03% and ≧80 and <120 Group II ≧90 and ≦0.03% and ≧80 and <120 Group III ≧90 and ≦0.03% and ≧120 Group IV All polyalphaolefins (PAO) Group V All Stocks Not included in Groups I-IV

Natural oils include animal oils, vegetable oils (castor oil and lard oil, for example), and mineral oils. Animal and vegetable oils possessing favorable thermal oxidative stability can be used. Of the natural oils, mineral oils are preferred. Mineral oils vary widely as to their crude source, for example, as to whether they are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal or shale are also useful in the present disclosure. Natural oils vary also as to the method used for their production and purification, for example, their distillation range and whether they are straight run or cracked, hydrorefined, or solvent extracted.

Group II and/or Group III hydroprocessed or hydrocracked base stocks, as well as synthetic oils such as polyalphaolefins, alkyl aromatics and synthetic esters, i.e. Group IV and Group V oils are also well known base stock oils. The Group III base stock is highly paraffinic with saturates level higher than 90%, preferably 95%, a viscosity index greater than 125, preferably greater than 135, or more preferably greater than 140, very low aromatics of 3%, preferably less than 1%, and aniline point of 118 or higher.

Synthetic oils include hydrocarbon oil such as polymerized and interpolymerized olefins (polybutylenes, polypropylenes, propylene isobutylene copolymers, ethylene-olefin copolymers, and ethylene-alphaolefin copolymers, for example). Polyalphaolefin (PAO) oil base stocks, the Group IV API base stocks, are a commonly used synthetic hydrocarbon oil. By way of example, PAOs derived from C₆, C₈, C₁₀, C₁₂, C₁₄, C₁₆ olefins or mixtures thereof may be utilized. See U.S. Pat. Nos. 4,956,122; 4,827,064; and 4,827,073, which are incorporated herein by reference in their entirety.

The API defines Group I stocks as solvent-refined mineral oils. Group I stocks contain the most saturates and sulfur and have the lowest viscosity indices. Group I defines the bottom tier of lubricant performance. Group II and III stocks are high viscosity index and very high viscosity index base stocks, respectively. The Group III oils contain fewer unsaturates and sulfur than the Group II oils. With regard to certain characteristics, both Group II and Group III oils perform better than Group I oils, particularly in the area of thermal and oxidative stability.

Group IV stocks consist of polyalphaolefins, which are produced via the catalytic oligomerization of linear alphaolefins (LAOs), particularly LAOs selected from C5-C14 alphaolefins, preferably from 1-hexene to 1-tetradecene, more preferably from 1-octene to 1-dodecene, and mixtures thereof, although oligomers of lower olefins such as ethylene and propylene, oligomers of ethylene/butene-1 and isobutylene/butene-1, and oligomers of ethylene with other higher olefins, as described in U.S. Pat. No. 4,956,122 and the patents referred to therein, and the like may also be used. PAOs offer superior volatility, thermal stability, and pour point characteristics to those base oils in Group I, II, and III.

Group V includes all the other base stocks not included in Groups I through IV. Group V base stocks includes the important group of lubricants based on or derived from esters. It also includes alkylated aromatics, polyinternal olefins (PIOs), polyalkylene glycols (PAGs), etc.

One of the benefits of the present disclosure is that it is applicable to base oils fitting into any of the above five categories, API Groups I to V, as well as other materials, such as described below. As used herein, whenever the terminology “Group . . . ” (followed by one or more of Roman Numerals I through V) is used, it refers to the API classification scheme set forth above.

PAOs are a class of hydrocarbons that can be manufactured by the catalytic oligomerization (polymerization to low-molecular-weight products) of linear α-olefin (LAO) monomers. These typically range from 1-octene to 1-dodecene, or 1-octene to 1-tetradecene, with 1-decene being a preferred material, although oligomeric copolymers of lower olefins such as ethylene and propylene may also be used, including copolymers of ethylene with higher olefins as described in U.S. Pat. No. 4,956,122 and the patents referred to therein, all of which are incorporated by reference in their entireties. PAO products have achieved importance in the lubricating oil market. Typically there are two classes of synthetic hydrocarbon fluids (SHF) produced from linear alphaolefins, the two classes of SHF being denoted as PAO and HVI-PAO (high viscosity index PAO's). PAO's of different viscosity grades are typically produced using promoted BF or AlCl₃ catalysts.

Specifically, PAOs may be produced by the polymerization of olefin feed in the presence of a catalyst, such as AlCl₃, BF₃, or promoted AlCl₃ or BF₃. Processes for the production of PAOs are disclosed, for example, in the following patents: U.S. Pat. Nos. 3,149,178; 3,382,291; 3,742,082; 3,769,363; 3,780,128; 4,172,855 and 4,956,122, which are fully incorporated herein by reference. PAOs are also discussed in the following: Will, J. G. Lubrication Fundamentals, Marcel Dekker: New York, 1980. Subsequent to polymerization, the PAO lubricant range products are typically hydrogenated in order to reduce the residual unsaturation, generally to a level of greater than 90% of hydrogenation. High viscosity PAO's may be conveniently made by the polymerization of an alpha-olefin in the presence of a polymerization catalyst such as Friedel-Crafts catalysts. These include, for example, boron trifluoride, aluminum trichloride, or boron trifluoride, promoted with water, with alcohols such as ethanol, propanol, or butanol, with carboxylic acids, or with esters such as ethyl acetate or ethyl propionate or ether such as diethyl ether, and diisopropyl ether. (See for example, the methods disclosed by U.S. Pat. Nos. 4,149,178 and 3,382,291.) Other descriptions of PAO synthesis are found in the following: U.S. Pat. No. 3,742,082; U.S. Pat. No. 3,769,363; U.S. Pat. No. 3,876,720; U.S. Pat. No. 4,239,930; U.S. Pat. No. 4,367,352; U.S. Patent No. 4,413,156; U.S. Pat. No. 4,434,408; U.S. Pat. No. 4,910,355; U.S. Pat. No. 4,956,122; and U.S. Pat. No. 5,068,487, all of which are incorporated in their entirety herein by reference.

Another class of HVI-PAOs may be prepared by the action of a supported, reduced chromium catalyst with an alpha-olefin monomer. Such PAOs are described in U.S. Pat. No. 4,827,073; U.S. Pat. No. 4,827,064; U.S. Pat. No. 4,967,032; U.S. Pat. No. 4,926,004; and U.S. Pat. No. 4,914,254. Commercially available PAOs include SpectraSyn™ 2, 4, 5, 6, 8, 10, 40, 100 and SpectraSyn Ultra™ 150, SpectraSyn Ultra™ 300, SpectraSyn Ultra™ 1000, etc. (ExxonMobil Chemical Company, Houston, Tex.). Also included are PAOs prepared the presence of a metallocene catalyst with a non-coordinating anion activator and hydrogen as discussed in U.S. Published Patent Application No. 2008/0177121.

Group V base stocks meeting the aforementioned viscosity criteria and preferably the aforementioned carbon numbers for a permissible fluid are preferred fluids. Group V includes esters that are a preferred embodiment of this disclosure. In a preferred embodiment, fluids according to the present disclosure may be selected from esters of mono and poly acids with monoalcohols or polyalcohols. Monobasic esters are preferred—they are the most readily available esters having viscosity sufficient to meet the criteria of a fluid according to the disclosure.

Esters are preferred lubricating oil base stocks of this disclosure. Solvency and seal compatibility characteristics may be secured by the use of esters such as the esters of dibasic acids with monoalkanols and the polyol esters of monocarboxylic acids. Esters of the former type include, for example, the esters of dicarboxylic acids such as phthalic acid, succinic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc., with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types of esters include dibutyl adipate, di-(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained by reacting one or more polyhydric alcohols, preferably the hindered polyols such as the neopentyl polyols; e.g., neopentyl glycol, trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylol propane, pentaerythritol and dipentaerythritol with alkanoic acids containing at least 4 carbon atoms, preferably C₅ to C₃₀ acids such as saturated straight chain fatty acids including caprylic acid, capric acids, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid, or the corresponding branched chain fatty acids or unsaturated fatty acids such as oleic acid, or mixtures of any of these materials.

Esters that meet the criteria of the disclosure may be selected from the reaction product of at least one C1 to C20 alcohols and at least one C1 to C20 carboxylic acids to prepare a variety of esters that would meet the criteria of this disclosure. The alcohols can be linear, cyclic, or branched. Near linear or less branched alcohols, such as described in U.S. Pat. Nos. 6,969,735, 6,969,736, and 6,982,295 are used as the esterifying alcohol(s) in preferred embodiments. The esters can contain additional oxygen in the form of ethers and other heteroatoms, like N, and S. They can be saturated or unsaturated. There can be more than one hydroxy group per molecule, so diols and triols are also considered, however monobasic acid esters are preferred and in still more preferred embodiments polyol esters are excluded from compositions according to the disclosure. The same would hold true for the carboxylic acids: linear, branched, cyclic, saturated, unsaturated, with or without other heteroatoms, mono or poly carboxylic acids, although monocarboxylic acids are preferred.

Some specific examples include the C8-C10 ester of pentanoic acid, C8-C10 ester of hexanoic acid, the C8-C10 ester of heptanoic acid, the C8-C10 ester of the C8-C10 acid, 2-ethylhexyl ester of C8-C10 acid, the isooctyl ester of C8-C10 acid, the isononyl ester of C8-C10 acid, pentaeyrithritol ester of C8-C10 acid, trimethylol propane ester of C8-C10, 2-ethylhexyl palmitate, isooctyl pentanoate, isononyl pentanoate, isononyl heptanoate, isooctyl isopentanoate, isononyl isopentanoate, 2-ethylhexyl 2-ethylhexanoate, isooctyl 2-ethylhexanoate, isononyl 2-ethylhexanoate, isononyl heptanoate, isooctyl heptanoate, isononyl isopentanoate, decyl heptanoate, nonyl heptanoate, ethyl decanoate, di-isooctyl adipate, neopentylglycol ester of pentanoic acid, the neopentylglycol ester of isopentanoic acid, neopentylglycol ester of heptanoic and nonanoic acid, etc. Some preferred embodiments include isononyl heptanoate, the C8-C10 ester of pentanoic acid, the C8-C10 ester of heptanoic acid, iso-octyl pentanoate, isononyl pentanoate, isooctyl heptanoate, isooctyl isopentoate, and isononyl pentanoate.

Group V basestock components can also include hydrocarbon-substituted aromatic compounds, such as long chain alkyl substituted aromatics, including alkylated naphthalenes, alkylated benzenes, alkylated diphenyl compounds and alkylated diphenyl methanes. While not critical to the characterization thereof, the carbon numbers of these are most preferably between C12 and C20.

Non-conventional or unconventional base stocks and/or base oils include one or a mixture of base stock(s) and/or base oil(s) derived from: (1) one or more Gas-to-Liquids (GTL) materials, as well as (2) hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock(s) and/or base oils derived from synthetic wax, natural wax or waxy feeds, mineral and/or non-mineral oil waxy feed stocks such as gas oils, slack waxes (derived from the solvent dewaxing of natural oils, mineral oils or synthetic oils; e.g., Fischer-Tropsch feed stocks), natural waxes, and waxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal crackates, foots oil or other mineral, mineral oil, or even non-petroleum oil derived waxy materials such as waxy materials recovered from coal liquefaction or shale oil, linear or branched hydrocarbyl compounds with carbon number of 20 or greater, preferably 30 or greater and mixtures of such base stocks and/or base oils.

GTL materials are materials that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks such as hydrogen, carbon dioxide, carbon monoxide, water, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butylenes, and butynes. GTL base stocks and/or base oils are GTL materials of lubricating viscosity that are generally derived from hydrocarbons; for example, waxy synthesized hydrocarbons, that are themselves derived from simpler gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks. GTL base stock(s) and/or base oil(s) include oils boiling in the lube oil boiling range (1) separated/fractionated from synthesized GTL materials such as, for example, by distillation and subsequently subjected to a final wax processing step which involves either or both of a catalytic dewaxing process, or a solvent dewaxing process, to produce lube oils of reduced/low pour point; (2) synthesized wax isomerates, comprising, for example, hydrodewaxed or hydroisomerized cat and/or solvent dewaxed synthesized wax or waxy hydrocarbons; (3) hydrodewaxed or hydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T) material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possible analogous oxygenates); preferably hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxy hydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (or solvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.

GTL base stock(s) and/or base oil(s) from GTL materials, especially, hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxed wax or waxy feed, preferably F-T material derived base stock(s) and/or base oil(s), are characterized typically as having kinematic viscosities at 100° C. of from 2 mm²/s to 50 mm²/s (ASTM D445). They are further characterized typically as having pour points of −5° C. to −40° C. or lower (ASTM D97). They are also characterized typically as having viscosity indices of 80 to 140 or greater (ASTM D2270).

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than 10 ppm, and more typically less than 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorous and aromatics make this materially especially suitable for the formulation of low SAP products.

The term GTL base stock and/or base oil and/or wax isomerate base stock and/or base oil is to be understood as embracing individual fractions of such materials of wide viscosity range as recovered in the production process, mixtures of two or more of such fractions, as well as mixtures of one or two or more low viscosity fractions with one, two or more higher viscosity fractions to produce a blend wherein the blend exhibits a target kinematic viscosity.

The GTL material, from which the GTL base stock(s) and/or base oil(s) is/are derived is preferably an F-T material (i.e., hydrocarbons, waxy hydrocarbons, wax).

Base oils for use in the formulated lubricating oils useful in the present disclosure are any of the variety of oils corresponding to API Group I, Group II, Group III, Group IV and Group V oils and mixtures thereof, preferably API Group II, Group III, Group IV and Group V oils and mixtures thereof, more preferably the Group III to Group V base oils due to their exceptional volatility, stability, viscometric and cleanliness features. Minor quantities of Group I stock, such as the amount used to dilute additives for blending into formulated lube oil products, can be tolerated but should be kept to a minimum, i.e. amounts only associated with their use as diluent/carrier oil for additives used on an “as-received” basis. Even in regard to the Group II stocks, it is preferred that the Group II stock be in the higher quality range associated with that stock, i.e. a Group II stock having a viscosity index in the range 100<VI<120.

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) and hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than 10 ppm, and more typically less than 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorous and aromatics make this material especially suitable for the formulation of low sulfur, sulfated ash, and phosphorus (low SAP) products.

The lubricant compositions of this disclosure may contain other fluids in addition to the first and second fluids. For example, the lubricant compositions may have a third fluid that can be a high viscosity or low viscosity fluid, or other combinations of fluids.

The amount of fluids in the finished lubricants may not be solely governed by the resulting traction performance. Other properties such as flash point, viscosity, seal compatibility, demulsibility, foam and air release, paint and sealant compatibility and volatility among others will also have to be considered. This is within the skill of the ordinary artisan, in possession of the present disclosure.

In accordance with this disclosure, the second fluid is used (optionally with additives) to modify the traction of a high viscosity fluid, e.g., 320 cSt or greater fluid, by creating a blend where the second fluid (or mixture of second and third fluids and the like) is present in the amount of from 1 to 99 wt %, preferably from 5 to 95 wt %. In an embodiment, the first fluid is present in the blend in the amount of from 20 to 80 wt %, or from 30 to 70 wt %, or from 40 to 60 wt %, or from 45 to 55 wt %, based on the weight of the entire composition. The second fluid is present in the blend in the amount of from 20 to 80 wt %, or from 30 to 70 wt %, or from 40 to 60 wt %, or from 45 to 55 wt %, based on the weight of the entire composition. Ranges from any lower limit to any upper limit are also contemplated, so that, by way of additional examples, the first fluid may be present in the blend in the amount of from 5 to 55 wt %, or from 45 to 95 wt %, and so on, and the second fluid may be present in the blend in the amount of from 5 to 55 wt %, or from 45 to 95 wt %, and so on. Additional embodiments include first or second fluids according to the present disclosure present in the amount of 5 to less than 50 wt %, greater than 50 to 95 wt %, greater than 70 to 95 wt %. All weight percentages used herein are based on the weight of the final composition, unless otherwise specified.

Compositions according to the present disclosure are particularly useful in applications wherein there are EHL contacts that have a component of sliding. Examples include spherical roller bearings, deep groove ball bearings, angular contact bearings among others. Additionally, most gear systems contain multiple sliding EHL contacts between meshing gear teeth. Examples include spur gears, helical gears, hypoid gears, bevel bears, worm gears, and the like.

An embodiment of the disclosure comprises a blend at least one low viscosity fluid with at least one higher viscosity fluid. In a preferred embodiment, at least one lower viscosity fluid is blended with a higher viscosity fluid to yield a gear lubricant that is SAE 70 W or higher, based on the SAE J306 classification system. This classification system was designed to provide limits with respect to the kinematic viscosity at 100° C. and the Brookfield viscosity for automotive gear oils. Due to the nature of the fluids according to the present disclosure, when they are employed at concentrations where the traction coefficient of the final composition is significantly reduced relative to the traction coefficient of the higher viscosity fluid, cold temperature fluidity of the final composition is also affected because of the low viscosity of the second fluid. Consequently, the resulting gear lubricants that are formulated to contain the fluids described by this disclosure will, in embodiments, have significantly lower Brookfield viscosities than gear lubricants with similar kinematic viscosities that do not contain the fluids. Brookfield viscosities used herein are measure according to ASTM D-2983.

For industrial gears, one common type of gearing is worm gears. Worm gears form an extended elliptical contact against the wheel and operate under high sliding EHL conditions. Therefore, there is a significant benefit to low traction fluids in terms of energy savings.

Quantifying the amount of efficiency that can be expected is difficult because it is dependent on many factors, in worm gears for example, the amount of efficiency seen will depend on many factors including the shaft bearings, seals, churning losses, gear meshing, gear reduction ratios, etc. However, it is estimated that the gains may be substantial due to the high sliding and generally high energy losses. Steel gears are generally more efficient than bronze worm gears, and therefore, the absolute efficiency gains will be lessened.

Nevertheless, one of ordinary skill in the art can quantify fuel efficiency of a gear system by numerous methods and more particularly can determine an improvement in such system for embodiments of compositions according to the present disclosure compared with lubricant composition that do not show an improvement. Likewise, the energy efficiency of a machine operating said gear system can be readily determined and comparisons made.

Rolling element bearings have many configurations and depending on the type of configuration, there may or may not be a benefit to having a lower traction fluid. This may also be determined by one of ordinary skill in the art in possession of the present disclosure. Where there is sliding between the ball and the raceway, the oil is being sheared such that the reduced traction properties of the lubricants described in this disclosure will reduce the energy losses.

The present disclosure is particularly beneficial in any system that includes machine elements that contain gears of any kind and rolling element bearings. Examples of such systems include electricity generating systems, industrial manufacturing equipment such as paper, steel and cement mills, hydraulic systems, automotive drive trains, aircraft propulsion systems, etc. It will be recognized by one of ordinary skill in the art in possession of the present disclosure that the various embodiments set forth herein, including preferred and more preferred embodiments, may be combined in a manner consistent with achieving the Objectives of the present disclosure.

The lubricating composition is further characterized by a traction coefficient of less than 0.15, preferably from 0.15 to 0.0001, more preferably 0.015 to 0.001, measured over the operating range for determination of traction performance of 0.1 GPa to 3.5 GPa peak contact pressure, at −40° C. to 200° C. lubricant temperature and at % slide-to-roll ratios of greater than 1%, with a lubricant entraining velocity 0.25 m/s to 10 m/s; and also to compositions that do not contain PAO 2 or do not contain PAC 150, or do not contain PAO 2 and do not contain PAO 150; to compositions that contain GTL fluids and also to compositions that do not contain GTL fluids.

In an embodiment, the disclosure includes the mixing of one or more low viscosity fluids with one or more high viscosity fluids to provide lube weight fluids with low traction. These fluids may be combined with additive packages, thickeners, defoamants, VI improvers, pour point depressants, extreme pressure agents, anti-wear additives, demulsifiers, haze inhibitors, chromophores, anti-oxidants, dispersants, detergents, anti-rust additives, metal passivators, and the like, to provide lubricating oils for various automotive and industrial applications. The order of blending is not particularly critical and it will be recognized that adding a first fluid to a second fluid is substantially similar to adding the second fluid to the first fluid.

Other Additives

The formulated lubricating oil useful in the present disclosure may additionally contain one or more of the other commonly used lubricating oil performance additives including but not limited to dispersants, other detergents, corrosion inhibitors, rust inhibitors, metal deactivators, other anti-wear agents and/or extreme pressure additives, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, other friction modifiers, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, and others. For a review of many commonly used additives, see Klamann in Lubricants and Related Products, Verlag Chemie, Deerfield Beach, Fla.; ISBN 0-89573-177-0. Reference is also made to “Lubricant Additives” by M. W. Ranney, published by Noyes Data Corporation of Parkridge, N.J. (1973).

The types and quantities of performance additives used in combination with the instant disclosure in lubricant compositions are not limited by the examples shown herein as illustrations.

Viscosity Modifiers/Improvers

The lubricant compositions disclosed herein may also include one or more viscosity modifiers/viscosity improvers as part of the lubricant composition. Viscosity modifiers (also known as Viscosity Index modifiers, VI modifiers, Viscosity index improvers, and VI improvers) increase the viscosity of the oil composition at elevated temperatures which increases film thickness, while having limited effect on viscosity at low temperatures.

Suitable viscosity improvers include high molecular weight hydrocarbons, polyesters and viscosity index improver dispersants that function as both a viscosity index improver and a dispersant. Typical molecular weights of these polymers are between 10,000 to 1,000,000, more typically 20,000 to 500,000, and even more typically between 50,000 and 200,000.

Examples of suitable viscosity improvers are polymers and copolymers of methacrylate, butadiene, olefins, or alkylated styrenes. Polyisobutylene is a commonly used viscosity index improver. Another suitable viscosity index improver is polymethacrylate (copolymers of various chain length alkyl methacrylates, for example), some formulations of which also serve as pour point depressants. Other suitable viscosity index improvers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (copolymers of various chain length acrylates, for example). Specific examples include styrene-isoprene or styrene-butadiene based polymers of 50,000 to 200,000 molecular weight.

The amount of viscosity modifier may range from zero to 25 wt or 0.2 to 20 wt %, or advantageously 3 to 15 wt %, or more advantageously 5 to 13 wt %, or still more advantageously 6 to 10 wt %, based on active ingredient and depending on the specific viscosity modifier used. In one particularly advantageous form, the viscosity modifier is an olefin copolymer viscosity modifier at 3 to 15 wt %, or 5 to 13 wt %, or 6 to 10 wt % of the lubricant composition. In one particularly advantageous form, the lubricant compositions disclosed herein include 6 to 7 wt % of an olefin copolymer viscosity modifier.

Additive Package

The lubricant compositions disclosed herein may also include an additive package including a combination of antioxidants, dispersants, detergents and antiwear agents. Further details on these additives are included below. The additive package may be included in the lubricant compositions at from 2 to 30 wt. %, 10 to 25 wt %, or 13 to 23 wt %, or 15 to 20 wt % of the lubricant composition. In one particularly advantageous form, the additive package is included at 17 wt % of the lubricant composition. One non-limiting exemplary additive package that includes the above combination of additives is supplied by Infineum and is designated Infineum D3426.

Antioxidants

Typical anti-oxidant include phenolic anti-oxidants, aminic anti-oxidants and oil-soluble copper complexes.

The phenolic antioxidants include sulfurized and non-sulfurized phenolic antioxidants. The terms “phenolic type” or “phenolic antioxidant” used herein includes compounds having one or more than one hydroxyl group bound to an aromatic ring which may itself be mononuclear, e.g., benzyl, or poly-nuclear, e.g., naphthyl and spiro aromatic compounds. Thus “phenol type” includes phenol per se, catechol, resorcinol, hydroquinone, naphthol, etc., as well as alkyl or alkenyl and sulfurized alkyl or alkenyl derivatives thereof, and bisphenol type compounds including such bi-phenol compounds linked by alkylene bridges sulfuric bridges or oxygen bridges. Alkyl phenols include mono- and poly-alkyl or alkenyl phenols, the alkyl or alkenyl group containing from 3-100 carbons, preferably 4 to 50 carbons and sulfurized derivatives thereof, the number of alkyl or alkenyl groups present in the aromatic ring ranging from 1 to up to the available unsatisfied valences of the aromatic ring remaining after counting the number of hydroxyl groups bound to the aromatic ring.

Generally, therefore, the phenolic anti-oxidant may be represented by the general formula:

(R)_(x)—Ar—(OH)_(y)

where Ar is selected from the group consisting of:

wherein R is a C₃-C₁₀₀ alkyl or alkenyl group, a sulfur substituted alkyl or alkenyl group, preferably a C₄-C₅₀ alkyl or alkenyl group or sulfur substituted alkyl or alkenyl group, more preferably C₃-C₁₀₀ alkyl or sulfur substituted alkyl group, most preferably a C₄-C₅₀ alkyl group, R^(g) is a C₁-C₁₀₀ alkylene or sulfur substituted alkylene group, preferably a C₂-C₅₀ alkylene or sulfur substituted alkylene group, more preferably a C₂-C₂ alkylene or sulfur substituted alkylene group, y is at least 1 to up to the available valences of Ar, x ranges from 0 to up to the available valances of Ar-y, z ranges from 1 to 10, n ranges from 0 to 20, and m is 0 to 4 and p is 0 or 1, preferably y ranges from 1 to 3, x ranges from 0 to 3, z ranges from 1 to 4 and n ranges from 0 to 5, and p is 0.

Preferred phenolic anti-oxidant compounds are the hindered phenolics and phenolic esters which contain a sterically hindered hydroxyl group, and these include those derivatives of dihydroxy aryl compounds in which the hydroxyl groups are in the o- or p-position to each other. Typical phenolic anti-oxidants include the hindered phenols substituted with C₁+ alkyl groups and the alkylene coupled derivatives of these hindered phenols. Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl phenol; 2-methyl-6-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4 methyl phenol; 2,6-di-t-butyl-4-ethyl phenol; and 2,6-di-t-butyl 4 alkoxy phenol; and

Phenolic type anti-oxidants are well known in the lubricating industry and commercial examples such as Ethanox® 4710, Irganox® 1076, Irganox® L1035, Irganox® 1010, Irganox® L109, Irganox® L118, Irganox®L135 and the like are familiar to those skilled in the art. The above is presented only by way of exemplification, not limitation on the type of phenolic anti-oxidants which can be used.

The phenolic anti-oxidant can be employed in an amount in the range of 0 to 3 wt %, preferably 0.25 to 2.5 wt %, more preferably 0.5 to 2 wt % on an active ingredient basis.

Aromatic amine anti-oxidants include phenyl-α-naphthyl amine which is described by the following molecular structure:

wherein R^(z) is hydrogen or a C₁ to C₁₄ linear or C₃ to C₁₄ branched alkyl group, preferably C₁ to C₁₀ linear or C₃ to C₁₀ branched alkyl group, more preferably linear or branched C₆ to C₈ and n is an integer ranging from 1 to 5 preferably 1. A particular example is Irganox L06.

Other aromatic airline anti-oxidants include other alkylated and non-alkylated aromatic amines such as aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic, aromatic or substituted aromatic group, R⁹ is an aromatic or a substituted aromatic group, and R¹⁰ is H, alkyl, aryl or R¹¹S(O)_(x)R¹² where R¹¹ is an alkylene, alkenylene, or aralkylene group, R¹² is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R⁸ may contain from 1 to 20 carbon atoms, and preferably contains from 6 to 12 carbon atoms. The aliphatic group is a saturated aliphatic group. Preferably, both R⁸ and R⁹ are aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joined together with other groups such as S.

Typical aromatic airlines anti-oxidants have alkyl substituent groups of at least 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups will not contain more than 14 carbon atoms. The general types of such other additional amine anti-oxidants which may be present include diphenylamines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Mixtures of two or more of such other additional aromatic amines may also be present. Polymeric amine antioxidants can also be used.

Another class of anti-oxidant used in lubricating oil compositions and which may also be present are oil-soluble copper compounds. Any oil-soluble suitable copper compound may be blended into the lubricating oil. Examples of suitable copper antioxidants include copper dihydrocarbyl thio- or dithio-phosphates and copper salts of carboxylic acid (naturally occurring or synthetic). Other suitable copper salts include copper dithiocarbamates, sulphonates, phenates, and acetylacetonates. Basic, neutral, or acidic copper Cu(I) and or Cu(II) salts derived from alkenyl succinic acids or anhydrides are known to be particularly useful.

Such anti-oxidants may be used individually or as mixtures of one or more types of anti-oxidants, the total amount employed being an amount of 0.20 to 6 wt %, or 0.50 to 5 wt %, or 0.75 to 3 wt % (on an as-received basis). Mixed ashless antioxidants are often preferred, including those chosen from aminic antioxidants and hindered phenolic antioxidants.

Detergents

In addition to the alkali or alkaline earth metal salicylate detergent which is an optional component in the present disclosure, other detergents may also be present. While such other detergents can be present, it is preferred that the amount employed be such as to not interfere with the synergistic effect attributable to the presence of the salicylate. Therefore, most preferably such other detergents are not employed.

If such additional detergents are present, they can include alkali and alkaline earth metal phenates, sulfonates, carboxylates, phosphonates and mixtures thereof. These supplemental detergents can have total base number (TBN) ranging from neutral to highly overbased, i.e. TBN of 0 to over 500, preferably 2 to 400, more preferably 5 to 300, and they can be present either individually or in combination with each other in an amount in the range of from 0 to 10 wt %, preferably 0.5 to 5 wt % (active ingredient) based on the total weight of the formulated lubricating oil. Furthermore, mixtures of neutral detergents and overbased detergents may be useful.

Such additional other detergents include by way of example and not limitation calcium phenates, calcium sulfonates, magnesium phenates, magnesium sulfonates and other related components (including borated detergents).

Another optional component of the present lubricant compositions is one or more neutral/low TBN or mixture of neutral/low TBN and overbased/high TBN alkali or alkaline earth metal alkylsalicylate, sulfonate and/or phenate detergent preferably neutral/low TBN alkali or alkaline earth metal salicylate and at least one overbased/high TBN alkali or alkalene earth metal salicylate or phenate, and optionally one or more additional neutral and/or overbased alkali or alkaline earth metal alkyl sulfonate, alkyl phenolate or alkylsalicylate detergent, the detergent or detergent mixture being employed in the lubricant composition in an amount sufficient to achieve a sulfated ash content for the finished lubricant of 0.1 mass % to 2.0 mass %, preferably 0.1 to 1.5 mass %, more preferably 0.1 to 1.0 mass %, most preferably 0.1 to 0.7 mass %.

The TBN of the neutral/low TBN alkali or alkaline earth metal alkyl salicylate, alkyl phenate or alkyl sulfonate is 150 or less mg KOH/g of detergent, preferably 120 or less mg KOH/g, most preferably 100 or less mg KOH/g while the TBN of the overbased/high TBN alkali or alkaline earth metal alkyl salicylate, alkyl phenate or alkyl sultanate is 160 or more mg KOH/g, preferably 190 or more mg KOH/g, most preferably 250 or more mg KOH/g, TBN being measured by ASTM D-2896.

The mixture of detergents may be added to the lubricant composition in an amount up to 10 vol % based on active ingredient in the detergent mixture, preferably in an amount up to 8 vol % based on active ingredient, more preferably up to 6 vol % based on active ingredient in the detergent mixture, most preferably between 1.5 to 5.0 vol %, based on active ingredient in the detergent mixture.

By active ingredient is meant the amount of additive actually constituting the name detergent or detergent mixture chemicals in the formulation as received from the additive supplier, less any diluent oil included in the material. Additives are typically supplied by the manufacturer dissolved, suspended in or mixed with diluent oil, usually a light oil, in order to provide the additive in the more convenient liquid form. The active ingredient in the mixture is the amount of actual desired chemical in the material less the diluent oil.

Dispersants

During engine operation, oil-insoluble oxidation byproducts are produced. Dispersants help keep these byproducts in solution, thus diminishing their deposition on metal surfaces. Dispersants may be ashless or ash-forming in nature. Preferably, the dispersant is ashless. So called ashless dispersants are organic materials that form substantially no ash upon combustion. For example, non-metal-containing or borated metal-free dispersants are considered ashless. In contrast, metal-containing detergents discussed above form ash upon combustion.

Suitable dispersants typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

A particularly useful class of dispersants are the alkenylsuccinic derivatives, typically produced by the reaction of a long chain substituted alkenyl succinic compound, usually a substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of dispersant are well known commercially and in the literature. Exemplary U.S. patents describing such dispersants are U.S. Pat. Nos. 3,172,892; 3,2145,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersant are described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. A further description of dispersants may be found, for example, in European Patent Application No. 471 071, to which reference is made for this purpose.

Hydrocarbyl-substituted succinic acid compounds are popular dispersants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful.

Succinimides are formed by the condensation reaction between alkenyl succinic anhydrides and amines. Molar ratios can vary depending on the amine or polyamine. For example, the molar ratio of alkenyl succinic anhydride to TEPA can vary from 1:1 to 5:1.

Succinate esters are formed by the condensation reaction between alkenyl succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of an alkenyl succinic anhydride and pentaerythritol is a useful dispersant.

Succinate ester amides are formed by condensation reaction between alkenyl succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine.

The molecular weight of the alkenyl succinic anhydrides will typically range between 800 and 2,500. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid, and boron compounds such as borate esters or highly borated dispersants. The dispersants can be borated with from 0.1 to 5 moles of boron per mole of dispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols, formaldehyde, and amines. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500 or more.

Typical high molecular weight aliphatic acid modified Mannich condensation products can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HN(R)₂ group-containing reactants.

Examples of high molecular weight alkyl-substituted hydroxyaromatic compounds are polypropylphenol, polybutylphenol, and other polyalkylphenols. These polyalkylphenols can be obtained by the alkylation, in the presence of an alkylating catalyst, such as BF₃, of phenol with high molecular weight polypropylene, polybutylene, and other polyalkylene compounds to give alkyl substituents on the benzene ring of phenol having an average 600-100,000 molecular weight.

Examples of HN(R)₂ group-containing reactants are alkylene polyamines, principally polyethylene polyamines. Other representative organic compounds containing at least one HN(R)₂ group suitable for use in the preparation of Mannich condensation products are well known and include the mono- and di-amino alkanes and their substituted analogs, e.g., ethylamine and diethanol amine; aromatic diamines, e.g., phenylene diamine, diamino naphthalenes; heterocyclic amines, e.g., morpholine, pyrrole, pyrrolidine, imidazole, imidazolidine, and piperidine; melamine and their substituted analogs.

Examples of alkylene polyamine reactants include ethylenediamine, diethylene triamine, triethylene tetraamine, tetraethylene pentaamine, pentaethylene hexamine, hexaethylene heptaamine, heptaethylene octaamine, octaethylene nonaamine, nonaethylene decamine, and decaethylene undecamine and mixture of such amines having nitrogen contents corresponding to the alkylene polyamines, in the formula H₂N—(Z—NH—)_(n)H, mentioned before, Z is a divalent ethylene and n is 1 to 10 of the foregoing formula. Corresponding propylene polyamines such as propylene diamine and di-, tri-, tetra-, pentapropylene tri-, tetra-, penta- and hexaamines are also suitable reactants. The alkylene polyamines are usually obtained by the reaction of ammonia and dihalo alkanes, such as dichloro alkanes. Thus the alkylene polyamines obtained from the reaction of 2 to 11 moles of ammonia with 1 to 10 moles of dichloroalkanes having 2 to 6 carbon atoms and the chlorines on different carbons are suitable alkylene polyamine reactants.

Aldehyde reactants useful in the preparation of the high molecular products useful in this disclosure include the aliphatic aldehydes such as formaldehyde (also as paraformaldehyde and formalin), acetaldehyde and aldol (3-hydroxybutyraldehyde). Formaldehyde or a formaldehyde-yielding reactant is preferred.

Preferred dispersants include borated and non-borated succinimides, including those derivatives from mono-succinimides, his-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from 500 to 5000 or more or a mixture of such hydrocarbylene groups. Other preferred dispersants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components. Such additives may be used in an amount of 0.1 to 20 wt %, preferably 0.1 to 8 wt %, more preferably 1 to 6 wt % (on an as-received basis) based on the weight of the total lubricant.

Pour Point Depressants

Conventional pour point depressants (also known as lube oil flow improvers) may also be present. Pour point depressant may be added to lower the minimum temperature at which the fluid will flow or can be poured. Examples of suitable pour point depressants include alkylated naphthalenes polymethacrylates, polyacrylates, polyarylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers. Such additives may be used in amount of 0.0 to 0.5 wt %, preferably 0 to 0.3 wt %, more preferably 0.001 to 0.1 wt % on an as-received basis.

Corrosion Inhibitors/Metal Deactivators

Corrosion inhibitors are used to reduce the degradation of metallic parts that are in contact with the lubricating oil composition. Suitable corrosion inhibitors include aryl thiazines, alkyl substituted dimercapto thiodiazoles thiadiazoles and mixtures thereof. Such additives may be used in an amount of 0.01 to S wt %, preferably 0.01 to 1.5 wt %, more preferably 0.01 to 0.2 wt %, still more preferably 0.01 to 0.1 wt % (on an as-received basis) based on the total weight of the lubricating oil composition.

Seal Compatibility Additives

Seal compatibility agents help to swell elastomeric seals by causing a chemical reaction in the fluid or physical change in the elastomer. Suitable seal compatibility agents for lubricating oils include organic phosphates, aromatic esters, aromatic hydrocarbons, esters (butylbenzyl phthalate, for example), and polybutenyl succinic anhydride and sulfolane-type seal swell agents such as Lubrizol 730-type seal swell additives. Such additives may be used in an amount of 0.01 to 3 wt %, preferably 0.01 to 2 wt % on an as-received basis.

Anti-Foam Agents

Anti-foam agents may advantageously be added to lubricant compositions. These agents retard the formation of stable foams. Silicones and organic polymers are typical anti-foam agents. For example, polysiloxanes, such as silicon oil or polydimethyl siloxane, provide antifoam properties. Anti-foam agents are commercially available and may be used in conventional minor amounts along with other additives such as demulsifiers; usually the amount of these additives combined is less than 1 percent, preferably 0.001 to 0.5 wt %, more preferably 0.001 to 0.2 wt %, still more preferably 0.0001 to 0.15 wt % (on an as-received basis) based on the total weight of the lubricating oil composition.

Inhibitors and Antirust Additives

Anti-rust additives for corrosion inhibitors) are additives that protect lubricated metal surfaces against chemical attack by water or other contaminants. One type of anti-rust additive is a polar compound that wets the metal surface preferentially, protecting it with a film of oil. Another type of anti-rust additive absorbs water by incorporating it in a water-in-oil emulsion so that only the oil touches the surface. Yet another type of anti-rust additive chemically adheres to the metal to produce a non-reactive surface. Examples of suitable additives include zinc dithiophosphates, metal phenolates, basic metal sulfonates, fatty acids and amines. Such additives may be used in an amount of 0.01 to 5 wt %, preferably 0.01 to 1.5 wt % on an as-received basis.

Antiwear Agents

Antiwear agents or additives may also be included in the present disclosure. Non-limiting exemplary antiwear agents include ZDDP, zinc dithiocarbamates, molybdenum dialkyldithiophosphates, molybdenum dithiocarbamates, other organo molybdenum-nitrogen complexes, sulfurized olefins, etc.

A metal alkylthiophosphate and more particularly a metal dialkyl dithio phosphate in which the metal constituent is zinc, or zinc dialkyl dithio phosphate (ZDDP) may be present in the lubricating oils of the present disclosure. ZDDP can be primary, secondary or mixtures thereof ZDDP compounds generally are of the formula Zn[SP(S)(OR¹)(OR¹)(OR²)]₂ where R¹ and R² are C₁-C₁₈ alkyl groups, preferably C₂-C₁₂ alkyl groups. These alkyl groups may be straight chain or branched and can be derived from primary alcohols, secondary alcohols and mixtures thereof.

Preferable zinc dithiophosphates which are commercially available include secondary zinc dithiophosphates such as those available from for example, the Lubrizol Corporation under the trade designations “LZ 677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite under the trade designation “OLOA 262” and from, for example, Afton Chemical under the trade designation “HITEC 7169”.

The ZDDP is typically used in amounts of from 0.4 wt % to 1.2 wt %, preferably from 0.5 wt % to 1.0 wt %, and more preferably from 0.6 wt % to 0.8 wt %, based on the total weight of the lubricating oil, although more or less can often be used advantageously. Preferably, the ZDDP is a secondary ZDDP and present in an amount of from 0.6 to 1.0 wt % of the total weight of the lubricating oil.

The term “organo molybdenum-nitrogen complexes” embraces the organo molybdenum-nitrogen complexes described in U.S. Pat. No. 4,889,647. The complexes are reaction products of a fatty oil, dithanolamine and a molybdenum source. Specific chemical structures have not been assigned to the complexes. U.S. Pat. No. 4,889,647 reports an infrared spectrum for a typical reaction product of that disclosure; the spectrum identifies an ester carbonyl band at 1740 cm⁻¹ and an amide carbonyl band at 1620 cm⁻¹. The fatty oils are glyceryl esters of higher fatty acids containing at least 12 carbon atoms up to 22 carbon atoms or more. The molybdenum source is an oxygen-containing compound such as ammonium molybdates, molybdenum oxides and mixtures.

Other organo molybdenum complexes which can be used in the present disclosure are tri-nuclear molybdenum-sulfur compounds described in EP 1 040 115 and WO 99/31113 and the molybdenum complexes described in U.S. Pat. No. 4,978,464.

Friction Modifiers

A friction modifier is any material or materials that can alter the coefficient of friction of a surface lubricated by any lubricant or fluid containing such material(s). Friction modifiers, also known as friction reducers, or lubricity agents or oiliness agents, and other such agents that change the ability of base oils, formulated lubricant compositions, or functional fluids, to modify the coefficient of friction of a lubricated surface may be effectively used in combination with the base oils or lubricant compositions of the present disclosure if desired. Friction modifiers that lower the coefficient of friction are particularly advantageous in combination with the base oils and lube compositions of this disclosure. Friction modifiers may include metal-containing compounds or materials as well as ashless compounds or materials, or mixtures thereof. Metal-containing friction modifiers may include metal salts or metalligand complexes where the metals may include alkali, alkaline earth, or transition group metals. Such metal-containing friction modifiers may also have low-ash characteristics. Transition metals may include Mo, Sb, Sn, Fe, Cu, Zn, and others. Ligands may include hydrocarbyl derivative of alcohols, polyols, glycerols, partial ester glycerols, thiols, carboxylates, carbamates, thiocarbamates, dithiocarbamates, phosphates, thiophosphates, dithiophosphates, amides, imides, amines, thiazoles, thiadiazoles, dithiazoles, diazoles, triazoles, and other polar molecular functional groups containing effective amounts of O, N, S, or P, individually or in combination. In particular, Mo-containing compounds can be particularly effective such as for example Mo-dithiocarbamates, Mo(DTC), Mo-dithiophosphates, Mo(DTP), Mo-amines, Mo (Am), Mo-alcoholates, Mo-alcohol-amides, etc. See U.S. Pat. Nos. 5,824,627, 6,232,276, 6,153,564, 6,143;701, 6,110,878, 5,837,657, 6,010,987, 5,906,968, 6,734,150, 6,730,638, 6,689,725, 6,569,820; and also WO 99/66013; WO 99/47629; and WO 98/26030.

Ashless friction modifiers may also include lubricant materials that contain effective amounts of polar groups, for example, hydroxyl-containing hydrocarbyl base oils, glycerides, partial glycerides, glyceride derivatives, and the like. Polar groups in friction modifiers may include hydrocarbyl groups containing effective amounts of O, N, S or P, individually or in combination. Other friction modifiers that may be particularly effective include, for example, salts (both ash-containing and ashless derivatives) of fatty acids, fatty alcohols, fatty amides, fatty esters, hydroxyl-containing carboxylates, and comparable synthetic long-chain hydrocarbyl acids, alcohols, amides, esters, hydroxy carboxylates, and the like. In some instances fatty organic acids, fatty amines, and sulfurized fatty acids may be used as suitable friction modifiers.

Useful concentrations of friction modifiers may range from 0.01 weight percent to 10-15 weight percent or more, often with a preferred range of 0.1 weight percent to 5 weight percent. Concentrations of molybdenum-containing materials are of described in terms of Mo metal concentration. Advantageous concentrations of Mo may range from 10 ppm to 3000 ppm or more, and often with a preferred range of 20-2000 ppm, and in some instances a more preferred range of 30-1000 ppm. Friction modifiers of all types may be used alone or in mixtures with the materials of this disclosure. Often mixtures of two or more friction modifiers, or mixtures of friction modifier(s) with alternate surface active material(s), are also desirable.

Typical Amounts of Various Lubricant Oil Components Approximate wt % Compound Approximate wt % (useful) (preferred) Friction Modifiers  0.01-15 0.01-5 Antiwear Additives 0.01-6 0.01-4 Detergents 0.01-8 0.01-4 Dispersants  0.1-20  0.1-8 Antioxidants 0.01-5   0.01-1.5 Anti-foam Agents 0.001-1   0.001-0.1 Corrosion Inhibitors 0.01-5   0.01-1.5 Co-basestocks    0-50    0-40 Base Oils Balance Balance

The low and high viscosity fluid blends described herein have the ability to impart low traction characteristics to compositions incorporating the fluids. The use of these fluid blends are desirable in lubricant compositions in the presence of salicylate, sulfonate and phenate detergents, along with antioxidants and ashless antioxidants, along with succinimide based dispersants, along with zinc dialkyldithiophosphates, along with organic and metallic friction modifiers, along with corrosion inhibitors, and along with defoamants. The low and high viscosity fluid blends are useful in all lubricant applications.

In the above detailed description, the specific embodiments of this disclosure have been described in connection with its preferred embodiments. However, to the extent that the above description is specific to a particular embodiment or a particular use of this disclosure, this is intended to be illustrative only and merely provides a concise description of the exemplary embodiments. Accordingly, the disclosure is not limited to the specific embodiments described above, but rather, the disclosure includes all alternatives, modifications, and equivalents falling within the true scope of the appended claims. Various modifications and variations of this disclosure will be obvious to a worker skilled in the art and it is to be understood that such modifications and variations are to be included within the purview of this application and the spirit and scope of the claims.

The following are examples of the present disclosure and are not to be construed as limiting.

Examples

Various esters were obtained for traction coefficient testing. FIG. 1 lists some exemplary ester materials and their viscosity and traction coefficient. The esters include monoesters, diesters, neopentyl glycol (NPG) esters, trimethylolpropane (TMP) esters, pentaerithyritol (PE) esters, polyesters, and complex esters. The traction coefficient testing was conducted in accordance with the MTM TC Method. The viscosity of the esters was determined at 40° C. and 100° C. in accordance with ASTM D-445.

FIG. 2 graphically shows the dependence of traction coefficient on the composition of a polyalphaolefin (PAO) blend. Modal blending of PAOs in the prior art takes advantage of a plateau (mild increase) of traction as a high viscosity component is added to adjust viscosity.

A blend of Priolube™ ES 2087+ Synative™ ES 3235 was prepared. FIG. 3 graphically shows the dependence of traction coefficient on the blend composition of Priolube™ ES 2087+ Synative™ ES 3235. The blend composition showed a significant decrease of traction coefficient.

Various Priolube™ high viscosity complex esters available from Croda were blended with BASF polyol ester—Synative™ ES 3235 (16 cSt@40° C.) to a viscosity of 46 cSt. FIG. 4 graphically shows the dependence of traction coefficient on the composition of the various Priolube™ high viscosity complex esters. In each graph, the “y” axis is the traction coefficient and the “x” axis is the content of ester (wt. %). As shown in FIG. 4, some of the Priolube™ high viscosity complex esters provide bimodal effect when blended with low viscosity polyol ester (i.e., P 1929 and P2087). As also shown in FIG. 4, some of the Priolube™ high viscosity complex esters provide a synergistic effect when blended with low viscosity Synative™ ES 3235 (i.e., P1929).

Various high viscosity esters and low viscosity esters were blended together. FIG. 4 graphically shows the dependence of traction coefficient on the composition of various esters and ester blends. In each graph, the “y” axis is the traction coefficient and the “x” axis is the content of the high viscosity ester (wt. %) in the blend. As shown in FIG. 4, some of the high viscosity ester/low viscosity ester blends provide a synergistic effect (i.e., blends containing ES2917, P1847, ES2929 and P1929).

PCT and EP Clauses:

1. A method of reducing the traction coefficient of a lubricant composition, said method comprising blending a first fluid having a viscosity from 150 cSt to 2000 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.01 to 0.025 (MTM TC Method), with a second fluid having a viscosity from 1 cSt to 30 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.008 to 0.015 (MTM TC Method); wherein the second fluid is miscible with the first fluid; and wherein the traction coefficient of the lubricant composition is lower than the traction coefficient of the first fluid and the traction coefficient of second fluid, as determined by the MTM TC Method.

2. The method of clause 1 wherein the first fluid comprises a lubricating oil base stock selected from a Group I, II, III, IV or V base oil stock.

3 The method of clause 2 wherein the lubricating oil base stock comprises an ester base stock.

4. The method of clause 3 wherein the ester base stock comprises a monoester, a (diester, a neopentyl glycol (NPG) ester, a trimethylolpropane (TMP) ester, a pentaerithyritol (PE) ester, a polyester, or a complex ester.

5. The method of clause 1 wherein the second fluid comprises a lubricating oil base stock selected from a Group I, II, III, IV or V base oil stock.

6. The method of clause 5 wherein the lubricating oil base stock comprises an ester base stock.

7. The method of clause 6 wherein the ester base stock comprises a monoester, a diester, a neopentyl glycol (NPG) ester, a trimethylolpropane (TMP) ester, a pentaerithyritol (PE) ester, a polyester, or a complex ester.

8. The method of clauses 1-7 wherein the first fluid has a viscosity from 36 cSt to 125 cSt at 100° C. (ASTM D-445), and the second fluid has a viscosity from 1.3 cSt to 8 cSt at 100° C. (ASTM D-445).

9. The method of clauses 1-8 wherein the first fluid has a traction coefficient from 0.01 to 0.02, the second fluid has a traction coefficient from 0.008 to 0.011, and the lubricant composition has a traction coefficient from 0.015 to 0.001, all as determined by the MTM TC Method.

10. A lubricant composition comprising a first fluid having a viscosity from 150 cSt to 2000 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.01 to 0.025 (MTM TC Method), and a second fluid having a viscosity from 1 cSt to 30 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.008 to 0.015 (MTM TC Method); wherein the second fluid is miscible with the first fluid; and wherein the traction coefficient of the lubricant composition is lower than the traction coefficient of the first fluid and the traction coefficient of second fluid, as determined by the MTM TC Method.

11. The lubricant composition of clause 10 wherein the first fluid comprises a lubricating oil base stock selected from a Group I, II, III, IV or V base oil stock, and the second fluid comprises a lubricating oil base stock selected from a Group I, II, III, IV or V base oil stock.

12. The lubricant composition of clause 11 wherein the first fluid lubricating oil base stock comprises an ester base stock, and the second fluid lubricating oil base stock comprises an ester base stock.

13. The lubricant composition of clause 12 wherein the ester base stock comprises a monoester, a diester, a neopentyl glycol (NPG) ester, a trimethylolpropane (TMP) ester, a pentaerithyritol (PE) ester, a polyester, or a complex ester.

14. The lubricant composition of clauses 10-13 wherein the first fluid is present in an amount of 10 to 90 wt % of the lubricant composition, and the second fluid is present in an amount of 10 to 90 wt % of the lubricant composition.

15. The lubricant composition of clauses 10-14 which further comprises one or more of a viscosity improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, and anti-rust additive.

All patents and patent applications, test procedures (such as ASTM methods, UL methods, and the like), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. While the illustrative embodiments of the disclosure have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present disclosure, including all features which would be treated as equivalents thereof by those skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims. 

What is claimed is:
 1. A method of reducing the traction coefficient of a lubricant composition, said method comprising blending a first fluid having a viscosity from 150 cSt to 2000 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.01 to 0.025 (MTM TC Method), with a second fluid having a viscosity from 1 cSt to 30 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.008 to 0.015 (MTM TC Method); wherein the second fluid is miscible with the first fluid; and wherein the traction coefficient of the lubricant composition is lower than the traction coefficient of the first fluid and the traction coefficient of second fluid, as determined by the MTM TC Method.
 2. The method of claim 1 wherein the first fluid comprises a lubricating oil base stock selected from a Group I, II, III, IV or V base oil stock.
 3. The method of claim 2 wherein the lubricating oil base stock comprises an ester base stock.
 4. The method of claim 3 wherein the ester base stock comprises a monoester, a diester, a neopentyl glycol (NPG) ester, a trimethylolpropane (TMP) ester, a pentaerithyritol (PE) ester, a polyester, or a complex ester.
 5. The method of claim 1 wherein the second fluid comprises a lubricating oil base stock selected from a Group I, II, III, IV or V base oil stock.
 6. The method of claim 5 wherein the lubricating oil base stock comprises an ester base stock.
 7. The method of claim 6 wherein the ester base stock comprises a monoester, a diester, a neopentyl glycol (NPG) ester, a trimethylolpropane (TMP) ester, a pentaerithyritol (PE) ester, a polyester, or a complex ester.
 8. The method of claim 1 wherein the first fluid has a viscosity from 36 cSt to 125 cSt at 100° C. (ASTM D-445).
 9. The method of claim 1 wherein the second fluid has a viscosity from 1.3 cSt to 8 cSt at 100° C. (ASTM D-445).
 10. The method of claim 1 wherein the first fluid has a traction coefficient from 0.01 to 0.02, the second fluid has a traction coefficient from 0.008 to 0.011, and the lubricant composition has a traction coefficient from 0.015 to 0.001, all as determined by the MTM TC Method.
 11. The method of claim 1 wherein the first fluid is present in an amount of 10 to 90 wt % of the lubricant composition, and the second fluid is present in an amount of 10 to 90 wt % of the lubricant composition.
 12. A lubricant composition comprising a first fluid having a viscosity from 150 cSt to 2000 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.01 to 0.025 (MTM TC Method), and a second fluid having a viscosity from 1 cSt to 30 cSt at 40° C. (ASTM D-445) and a traction coefficient from 0.008 to 0.015 (MTM TC Method); wherein the second fluid is miscible with the first fluid; and wherein the traction coefficient of the lubricant composition is lower than the traction coefficient of the first fluid and the traction coefficient of second fluid, as determined by the MTM TC Method.
 13. The lubricant composition of claim 12 wherein the first fluid comprises a lubricating oil base stock selected from a Group I, II, III, IV or V base oil stock.
 14. The lubricant composition of claim 13 wherein the lubricating oil base stock comprises an ester base stock.
 15. The lubricant composition of claim 14 wherein the ester base stock comprises a monoester, a diester, a neopentyl glycol (NPG) ester, a trimethylolpropane (TMP) ester, a pentaerithyritol (PE) ester, a polyester, or a complex ester.
 16. The lubricant composition of claim 12 wherein the second fluid comprises a lubricating oil base stock selected from a Group I, II, III, IV or V base oil stock.
 17. The lubricant composition of claim 16 wherein the lubricating oil base stock comprises an ester base stock.
 18. The lubricant composition of claim 17 wherein the ester base stock comprises a monoester, a diester, a neopentyl glycol (NPG) ester, a trimethylolpropane (TMP) ester, a pentaerithyritol (PE) ester, a polyester, or a complex ester.
 19. The lubricant composition of claim 12 wherein the first fluid is present in an amount of 10 to 90 wt % of the lubricant composition, and the second fluid is present in an amount of 10 to 90 wt % of the lubricant composition.
 20. The lubricant composition of claim 12 which comprises a finished gear, transmission, engine or industrial lubricant.
 21. The lubricant composition of claim 20 which further comprises one or more of a viscosity improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, and anti-rust additive. 